The metallizing of thermoplastics, particularly of copolymers of acrylonitrile, butadiene and styrene is known. It is based on micro-roughening the plastic surface by an etching solution, seeding with a metal such as silver or palladium, whereby activation and sensitizing is brought about, electroless metal deposition (without current) of, for instance, copper or nickel and finally, electroplating according to conventional methods, copper usually being deposited as the first layer. As example of such known methods are found in the variants of the Noviganth process.
However, the electroplating of thermosetting plastics is technically difficult. Mechanical roughening methods are usually complicated and often, no fast-adhering metallization is obtained. It is known that thermosetting plastics can be chemically etched, particularly by an oxidizing attack. Subsequent metallizing as with thermoplastics is also possible. Chromic-sulfuric acid solutions are particularly well suited for roughening thermosetting plastics, particularly phenolic resins and unsaturated polyester resins. This method, while permitting the metallizing of thermosetting plastics, especially phenolic resin moldings, does not produce coatings that adhere sufficiently strongly for many applications. This manifests itself particularly in the case of hard chromium plating. As is well known, hard chromium films exhibit internal stresses. Metal combinations, e.g. copper-nickel-chromium on phenolic resin, tear away during the hard chromium plating, which is probably the result of insufficient adhesion.